1. Field of the Invention
The present invention relates generally to sewing machines and, in particular, to an improved side mount thread wiper installed in a sewing machine for withdrawing the severed thread from the path of the work piece following the application of a line of stitching.
2. Description of Related Art
In performing commercial sewing operations, it is necessary for maximum economy and efficiency to minimize the number of time-consuming hand operations. Among such time consuming manually performed operations is the removal of the excess or leftover severed thread, e.g. the tail, from the path of a work piece following completion of a sewing sequence so as to facilitate the unhindered performance of the sewing sequence for the next work piece. A thread-wiping or retracting mechanism pulls the excess thread above the presser foot so that the needle carries the tail below the presser foot and sews the tail in with the next stitch. Accordingly, the top surface of the next work piece is free from loose threads.
U.S. Pat. No. 3,901,171 discloses a thread wiper mounted behind the needle. Under normal sewing conditions the thread wiper is in a raised position rearwardly of the needle so as to be outside of the sewing or operating space of the sewing machine. Upon completion of a sewing stitch the needle is stopped in its fully raised position at which point the thread is cut. The thread wiper is thereafter lowered and passes between the needle and foot piece, whereupon the picker arm is swung across the path of the needle displacing the thread laterally. This thread wiper mechanism, however, is not suitable for use with heavy duty sewing machines that are used to sew heavier gauge materials, for example, carpet or upholstery, and include a walking foot synchronized with the needle during the stitching operation. An example heavy duty sewing machine is Model 767 manufactured by Durkopp Adler Ag. The distance between the walking foot and needle in such heavy duty sewing machines is too small to accommodate conventional thread wiper mechanisms.
It is therefore desirable to develop a thread wiper mechanism that is suitable for use with a heavy duty sewing machine having a walking foot.
The present invention is directed to an assembly for use with a sewing machine including a thread wiper adapted to be mountable to the side of the sewing machine.
In addition the invention relates to a thread wiper for use in a sewing machine having a needle reciprocatable along a path between a raised position and a lowered position. The thread wiper is mounted sidewardly relative to the needle and includes a picker arm, that while in a retracted position, is disposed sidewardly relative to said needle. Also included in the thread wiper is an actuating member supporting the picker arm. The actuating member performs the following operations: lowers the picker arm in a direction substantially parallel to the needle until a free end of the picker arm is at a level between the needle and the walking foot; sidewardly thrusts the picker arm at a first angle, relative to a vertical axis, towards the needle along a path between the needle and the walking foot without interference; advances further sideways the picker arm at a second angle, relative to the vertical axis, greater than the first angle; and retracts away while raising the picker member in a reverse movement to complete the cycle. In an alternative embodiment the same system can be used with a sewing machine that does not have a walking foot, but instead only has a presser foot.
Furthermore, the invention is directed to a method for cyclically operating the assembly described above. Initially, the picker arm is lowered in a direction substantially parallel to the needle until the free end of the picker arm is at a level between the needle and the walking foot. The picker arm is thrust sidewardly at a first angle, relative to a vertical axis, towards the needle along a path between the needle and the walking foot without interference. After being thrust sideward, the picker arm is advanced towards the needle at a second angle, relative to the vertical axis, greater than the first angle. Thereafter, the picker arm is retracted while being raised in a reverse movement to complete the cycle. As mentioned above with respect to the assembly, the method for operating the assembly may be performed when installed in a sewing machine that does not have a walking foot.
Another aspect of the invention is directed to an intelligent thread wiper for use with a sewing machine including a walking foot. The thread wiper includes a microprocessor for disabling (turning off) the thread wiper when the walking foot is set to a value greater than a predetermined percentage of a maximum permitted rise and/or the turn back operation of the sewing machine is disabled (turned off). Alternatively, the microprocessor may be programmed to enable (turn on) the thread wiper when the walking foot is set to a value less than a predetermined percentage of a maximum permitted rise and the turn back operation of the sewing machine is enabled (turned on).
In yet another embodiment the intelligent thread wiper may be used with a sewing machine that does not include a walking foot wherein the microprocessor is programmed to disable (turn off) the thread wiper when the turn back operation of the sewing machine is disabled (turned off). Conversely, the microprocessor may be programmed to enable (turn on) the thread wiper when the turn back operation of the sewing machine is enabled (turned on).
The invention is also directed to a sewing machine including a needle, a thread wiper mountable sidewardly relative to the needle and arranged so as not to interfere with the needle, and an end face plate covering the thread wiper.